The present invention relates to an apparatus for the inflation and deflation of air-filled bags, such as the dunnage bags commonly used to cushion cargo loads in truck trailers, railroad cars, and the like.
Inflatable dunnage bags are a common means of cushioning loads shipped via truck trailer, railroad car, or other typical shipping container, particularly where the cargo only partially fills the container and shifting during transport might cause damage. Typical dunnage bags in use today are constructed of one or more layers of paper surrounding a plastic lining. The paper serves to protect the bags from tearing, and thus a greater number of layers may be used in applications where the risk of damage to the dunnage bag is greater. A valve for filling the dunnage bag, usually constructed of plastic, is attached through a hole cut in the bag during manufacture. The bags are shipped flat from the manufacturer, and must be inflated by shipping personnel as containers are loaded with cargo.
The tools currently in use to fill dunnage bags with air are often simply converted tire inflation tools, which are attached to a hose leading from a source of compressed air. Some specialized tools are available for dunnage bag deflation, such as taught by U.S. Pat. No. 5,437,301 to Ramsey. In the use of such devices, the bag is first placed in the space that it will occupy as cargo is loaded into a container, and the inflation device is attached to the bag valve. The bag is then filled with air. until an appropriate air pressure within the bag is achieved. The inflation tool may connect with the bag valve through a ball-lock quick-disconnect attachment, which may be engaged and disengaged by simply sliding a ring on the attachment point up or down. Filling is thus a relatively simple operation, requiring only a few seconds of the operator's time.
A significant limitation of the current inflation tools is that they present no way to rapidly deflate a dunnage bag once the cargo is ready to be unloaded. The valve assembly in some such bags may be unscrewed to release air pressure within the bag, but because the bags are fairly rigid (owing to the protective paper covering) they tend not collapse simply due to the equalization of air pressure inside and outside of the bag. The bags cannot be quickly and conveniently reduced to a flat configuration such as they are shipped from the manufacturer. As a result, the standard industry practice is for shipping and receiving personnel to simply cut the bags with a utility knife in order to deflate them quickly for removal.
Dunnage bags are not reusable once cut, and thus they are generally considered to be a one-use, disposable commodity. Significant cost savings could be realized by the reuse of these dunnage bags. This could be rendered practical by devising a means to rapidly and easily deflate a dunnage bag without damaging the dunnage bag. The bags must be restored to the flat shape they held prior to their original use, so that they can be easily and compactly stored.
The prior art does include previous attempts to develop deflation tools for dunnage bags. U.S. Pat. No. 5,437,301 to Ramsey, discussed above, teaches a rotating valve actuator that selectively allows the flow of compressed air across an air passage connected to the dunnage bag in order to facilitate deflation. U.S. Pat. No. 6,053,222 to Peters teaches a dunnage bag deflation tool that uses a high-pressure air source to open the dunnage bag air valve, thereby allowing deflation, and also suck air out of the bag by discharging the air through a venturi tube. A venturi tube in its simplest form is an air passage with a region of restricted diameter. According to the Bernoulli inverse relationship between air velocity and pressure, passage of air through the restricted region of a venturi tube creates a low-pressure region. This low-pressure region results in a negative pressure or suction effect that may be used to draw air out of an attached container. Peters teaches two different embodiments of the deflation device, which differ by the means through which the device may be switched from inflation to deflation mode. One device calls for the operator to simply place a thumb over the venturi tube exit, thereby blocking that means of egress for the high-pressure air and directing the high-pressure air into the bag. The other embodiment incorporates a manually set bi-stable switch set at the entrance to the venturi tube, which prevents air from ever entering the venturi tube and thus forcing high-pressure air in the direction of the dunnage bag valve.
U.S. Pat. No. 5,454,407 to Huza et al. teaches another apparatus to both inflate and deflate a dunnage bag. This device incorporates the venturi effect as part of an automatic pressure sensing system, but relies on hand pressure directly to the dunnage bag for deflation. Other devices to inflate and deflate different types of chambers are known in the art, such as that taught by U.S. Pat. No. 5,947,168 to Viard for inflation and deflation of an air mattress.
Each of these devices suffers from important limitations. While the Peters device allows for the inflation and deflation of a dunnage bag using an integrated tool, its control mechanisms are of limited practicality. The operator of such a device should ideally be able to quickly turn on and off the source of high-pressure air, and quickly adjust the mode setting of the device to either inflate or deflate a dunnage bag. Ideally, the necessary controls would be simple and easily manipulated. The use of the operator's thumb to maintain the Peters device in the inflation mode would quickly result in operator fatigue. Given the large number of cargo containers that may be loaded and unloaded in a typical shipping facility during an operator's work shift, this rudimentary control mechanism would quickly prove unworkable. The use of a switch at the entrance of the venturi tube is an improvement, but because of its design and position on the device would be prone to failure. Furthermore, the overall design of the device lacks any means of dissipating or quieting the flow of high-pressure air out of the venturi tube during deflation of a dunnage bag; it would result in a violent burst of air moving directly toward the operator. This situation raises significant safety concerns. The air escaping in this manner would also create a great deal of noise, which may be not only uncomfortable for the operator but also may raise a safety issue itself. Finally, the design of the device does not incorporate any convenient means of holding the device during inflation and deflation; this is an important safety concern as well, since if the valve connection should fail then the device would be propelled backward at great speed due to force of air. In this situation, the device would likely swing in an arc due to the attached (but flexible) air hose, and could strike the operator or a bystander with great force, potentially causing severe injury or property damage.
The limitations of the prior art are overcome by the present invention as described below.